java websocket实现长连接,附加代码实现

Java中可以使用Java WebSocket API实现WebSocket长连接。下面是一个简单的示例代码：

服务端代码：

import java.io.IOException;
import java.net.InetSocketAddress;

import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint("/websocket")
public class WebSocketServer {

    private Session session;

    @OnOpen
    public void onOpen(Session session) {
        this.session = session;
        System.out.println("WebSocket opened: " + session.getId());
    }

    @OnMessage
    public void onMessage(String message) {
        System.out.println("Message received: " + message);
        try {
            session.getBasicRemote().sendText("Received message: " + message);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @OnClose
    public void onClose() {
        System.out.println("WebSocket closed");
    }

    @OnError
    public void onError(Throwable t) {
        System.out.println("WebSocket error: " + t.getMessage());
    }

    public static void main(String[] args) throws Exception {
        org.glassfish.tyrus.server.Server server = new org.glassfish.tyrus.server.Server("localhost", 8080, "/websocket", WebSocketServer.class);
        server.start();
        System.out.println("WebSocket server started");
        Thread.currentThread().join();
    }
}

客户端代码：

import java.net.URI;

import javax.websocket.ClientEndpoint;
import javax.websocket.CloseReason;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.WebSocketContainer;

@ClientEndpoint
public class WebSocketClient {

    private Session session;

    @OnOpen
    public void onOpen(Session session) {
        this.session = session;
        System.out.println("WebSocket opened: " + session.getId());
    }

    @OnMessage
    public void onMessage(String message) {
        System.out.println("Message received: " + message);
    }

    @OnClose
    public void onClose(CloseReason reason) {
        System.out.println("WebSocket closed: " + reason);
    }

    @OnError
    public void onError(Throwable t) {
        System.out.println("WebSocket error: " + t.getMessage());
    }

    public static void main(String[] args) throws Exception {
        WebSocketContainer container = javax.websocket.ContainerProvider.getWebSocketContainer();
        WebSocketClient client = new WebSocketClient();
        container.connectToServer(client, new URI("ws://localhost:8080/websocket"));
        System.out.println("WebSocket client started");
    }
}

这个示例代码使用了Tyrus作为WebSocket实现，可以使用Maven添加依赖：

<dependency>
    <groupId>org.glassfish.tyrus.bundles</groupId>
    <artifactId>tyrus-standalone-client</artifactId>
    <version>1.17.1</version>
</dependency>
<dependency>
    <groupId>org.glassfish.tyrus.bundles</groupId>
    <artifactId>tyrus-standalone-server</artifactId>
    <version>1.17.1</version>
</dependency>

当然，也可以使用其他的Java WebSocket实现库。